Automobile engines for example have hitherto been provided with a mechanism for circulating a lubricant (oil) around predetermined parts to ensure a smooth motion of the moving portions, although the lubricating oil may degrade with use and with the elapse of time and lose its desired lubricating properties or may permit a mixing of abrasive powders or sludge into the oil. For this reason, used oil must be changed at a certain interval (commonly, at every travel through a certain distance of the order of 3000 to 5000 kilometers) from the viewpoint of preventing any damage of the engine body, etc.
FIG. 16 is a schematic diagram for explaining an example of a conventional typical engine having a structure for changing the used oil, in which oil 100 residing within an oil pan 102 provided below a crankcase is supplied to a predetermined region by means of an oil pump 101. The oil is delivered under pressure by the pump 101 and is pressure regulated by a regulating valve 103, after which it is cleaned off by removing, by a filter 104, metal powder, carbon, sludge or other foreign matters which have been mixed into the oil. After having lubricated the parts of the engine, the oil is returned to the oil pan 102. Incidentally, the oil pan 102 is typically structured to be filled with oil.
In this manner, the oil is subjected to the cleaning process for removing the mixed substance by the filter 104 in the course of its circulation, although the removal of the foreign matters by use of the filter is limitative, with the inevitable problem that the oil itself tends to have a degraded property with the elapse of time. Therefore, the oil is changed through the operations removing a stopcock (drain cock) 106 from a hole (drain hole) 105 which is provided in the bottom of the oil pan 102 but is usually stopped, to drain off the used oil through a natural oil drain, and then stopping the hole 105 to allow new oil to be fed from the top.
By the way, in the case of automobiles supplied by automobile manufacturers to the market, it is common for the oil drain hole 105 provided in the oil pan below the engine to be stopped with a simple threaded stopcock 106. For this reason, in the oil change operations, the stopcock 105 is removed from the oil drain hole 105 as described above at the beginning thereof and, after the oil drain, the stopcock is screwed thereinto, which operations are cumbersome, resulting inevitably in the workers covered with oil. In the case of service factories, etc., in which the automobiles are raised by a lift for the oil draining operation, the operation is relatively easy to perform, although the problem that the workers may be dirtied with oil can not be solved. Alternatively, in case of the execution without the lift, the workers must crawl into a narrow space below the automobile to remove the stopcock from the oil pan bottom or screw it thereinto, which operation is also extremely cumbersome.
As described hereinabove, the conventional oil changing operations have had a deficiency in its workability and posed a problem that the workers or environments may be dirtied with oil.
Thus, taken as measures for eliminating the operative deficiencies is an operation draining off the oil from the top of the engine. This includes for example a method in which an elongated suction tube is inserted into a mounting hole for an oil gauge provided for checking the amount or dirtiness of the engine oil, to thereby vacuum suck the used oil, or a method in which the suction tube is inserted through an oil supply port (these methods are hereinafter referred to as "top drain methods").
However, those top drain methods have no expedient for verifying that the tube extremity has reached the bottom of the oil pan since the tube is inserted from above a crankshaft or other complicated mechanism which is accommodated within a narrow space in a dense manner. It is therefore difficult to drain off all amount of the oil, which may incur a problem that the insufficient drain of the used oil is not recognized until an oil check is made after the supply of new oil, or in extreme cases, a problem that the oil changing operation must be made again. The top drain method is not necessarily prevailing with its deficiency that it is difficult to remove metal powders or the like deposited on the bottom of the oil pan.
On the other hand, the method of draining the used oil from the bottom is advantageous in that the drain of all amount of oil is feasible. Thus, there are proposed methods of eliminating the deficiency of dirtiness with oil while keeping the advantage of the bottom drain method. More specifically, proposed are an oil changing method using a permanently fixed plug with a built-in normally-closed poppet valve (U.S. Pat. No. 4,745,894 (Japanese Official Gazette corresponding thereto: Japanese Patent Pub. No. Hei4-48,987)) and an oil changing method using a permanently fixed plug with a built-in normally-closed ball valve (U.S. Pat. No. 5,048,578, Japanese Patent Laid-open Pub. No. Hei8-170,782).
These methods are described as follows by way of the case using the plug with a built-in ball valve for example. That is, as illustrated in FIGS. 17 and 18, an existing oil drain hole stopcock having a simple plug structure is removed, and instead, a valved plug (stopcock) 201 with a built-in normally-closed ball valve is secured to an oil drain hole 105. Then, upon the oil change, a dedicated jig 204 is fitted to the plug 201 with the normally-closed ball valve to open the ball valve so that oil 100 within the oil pan 102 is sucked by a negative pressure. After the completion of the drain, the jig 204 is removed to again close the ball valve so that the new oil 100 is filled thereinto. It is to be noted that the suction drain of the oil 100 upon the release of the ball valve is compulsorily made through an oil drain hose 205 by means of a suction device 206.
This method allows the suction drain of oil by use of the valved plug 201 to be performed through the switching between opening and closing of the valve, so that there is no need for the operation of the removal of the plug and for the operation of rescrewing. It is thus possible to simplify the operation by use of the dedicated jig 204 causing the opening or closing of the ball valve as well as to prevent the workers or environments to be dirtied with oil. Furthermore,since the plug can permanently be fixed, there is advantageously eliminated a possibility of collapsing the threads through the defective operations upon the screwing of the plug or the removal thereof.
Referring to FIG. 18, description is made of the detailed structure of the plug 201 with the ball valve and of the status of use of the same. That is, this plug 201 with the ball valve is of a cylindrical shape including a threaded stem 211 screwed into an oil drain hole (externally threaded hole) 105 of the oil pan 102 and including a spring receiving portion 212 projecting from the tip of the threaded stem 211, with the threaded stem 211 having at its rear end a screwing hexagonal bolt head 213 integral therewith. Note that the top of the spring receiving portion 212 is blocked by a plug 214 serving also as a spring support and that the circumferential wall of the base continuous with the threaded stem is formed with three radial holes 215 circumferentially apart from one another so as to ensure an inflow of the oil into the cylinder. Then, the interior of the cylinder of the threaded stem 211 is provided with a valve seat 217 which is stopped by a ball 216 so that a coiled spring 218 within the spring receiving portion 212 presses the ball 216 against the valve seat 217 to thereby normally close the valve portion (see FIG. 18(a)). It is to be appreciated that during the normal time, a protection cap 250 is fitted into an opening 2131 of the bolt head 213 to prevent a possible leakage of oil. On the contrary, in the event of releasing the ball valve, the protection valve 250 is removed, after which a ball pressing jig 220 (corresponding to the above dedicated jig 204) having a needle-type tip 221 is inserted through the opening 2131 of the bolt head 213 of the bolt member, to disengage the ball 216 from the valve seat 217 against the spring force of the coiled spring 218 to thereby open the flow passage (see FIG. 18(b) and (c)). The ball valve is released in this manner, with the result that as indicated by an arrow of FIG. 18(c), the oil 100 within the oil pan 102 is sucked from the radial holes 215 provided in the circumferential wall of the spring receiving portion 212 at its base, through the valve portion of the ball valve and the passage 222 provided in the ball pressing jig 220, and via the tube 205 into the suction device 206.
On the other hand, the plug with the built-in poppet valve described in the U.S. Pat. No.4,745,849 corresponds to one having a valve head of a movable valve body in place of the ball valve of the above plug with the built-in ball valve. More specifically, the valved plug with the built-in poppet valve comprises a plug body which includes a cylindrical trunk portion extending through between the opposed ends and which is fixedly screwed into the oil pan, and a movable valve body which includes a valve head engaged with a valve seat which is the end of the plug body lying inside the oil pan, to close the valve passage, the movable valve body being urged by a spring force toward the direction closing the valve passage to normally close the valve passage.
Thus, in the same manner as the case of the plug with the built-in ball valve, the oil can be drained off by displacing the movable valve body against the spring force to open the valve passage.
The above-described bottom drain type oil changing method in which the conventional valved plug with the built-in ball valve or poppet valve is permanently secured to the oil drain hole will be advantageous over the other conventional methods in that the oil can promptly be drained from the oil pan with an easy operation and in that the metal powders or the like deposited on the bottom of the oil pan can be discharged.
However, the bottom drain type oil changing method using the valved plug with the built-in normally-closed valve having the above advantages suffers also from a problem to be improved in accordance with a recent change in the specifications of the oil pan. Furthermore, with a tendency toward a long-term use and long-traveling distance of the automobiles arising from the improvement in the automobile performances, it is desired to improve the durability of the valved stopcock and to ensure a secure drain irrespective of iteration of the used oil draining operations. It is also naturally expected to provide a low-cost plug capable of presenting the similar effect, and hence a plug having an even simpler structure is desired.
From the above points of view, the inventors have repeated wholehearted research and examination to conceive the present invention.
One of the above reasons of improvement lies in that although it was common in the prior art to fit the plug (stopcock, drain cock) for oil drain to the bottom of the oil pan 102, this structure may possibly break the drain plug in the event of contact (so-called "rubbing") of the bottom of the automobile with a projection on the ground. Thus, as shown in FIG. 19, recent tendency is toward the employment of a structure in which the plug 106 is fitted to the side wall (lateral wall surface) of the oil pan 102 in the vicinity of its bottom. In such a case, however, the oil to be drained off is limited to the oil residing above a line L of FIG. 19 due to the mounting position of the plug 106, with the result that the oil 110 or sludge may remain in the regions below the line L. In such a case, it may therefore be envisaged to insert a tube 111 from the top by the use of the top drain method as shown in FIG. 19 to perform the oil draining operation, although the top drain method entails the other problem described above. Furthermore, some types of automobiles may not permit the top drain method.
Another reason lies in a recent tendency toward a thinned wall of the oil pan from the viewpoint of the improvement in quality of materials, etc., even though there is employed a structure in which the drain cock is fitted to the bottom of the oil pan 102, which also poses a problem. That is, even the thinned oil pan requires a certain threaded hole length for fixedly screwing the drain cock, and hence backing materials 120 and 121 for the threaded hole are often fixed to the corresponding portions of the oil pan 102 as shown in FIG. 20 for example. However, even in the even to fusing the valved plug 201 proposed above, this will incur the same problem as described with reference to FIG. 19 since the line L in the diagram is the lower limit of the oil to be drained off as long as the plug is positioned in the bottom.
The present invention was conceived in order to further improve the prior art as described above. It is therefore an object of the present invention to provide a valved plug with a built-in normally-closed valve for an oil drain device, which ensures not merely an insertion of a flexible oil drain tube into the interior of an oil pan for a secure execution of the oil drain, but also a secure and smooth inserting operation without the tube being caught.
It is another object to provide a valved plug with a built-in normally-closed valve having an even simpler structure.
A further object of the present invention is to provide an oil drain device capable of securely draining off oil which may possibly remain on the bottom within an oil storing vessel such as an oil pan.